project suggestions

I have a client/friend who owns a plumbing/fixture supply
business. He is in the process of moving to another building
because of his growth/success. His entire business operates
on thousands and thousands of Excel spreadsheets. Every time
you go to sell a fixture(s) a spreadsheet is created from a template,
and that becomes the scratch sheet for a bid, then the invoice.
It really is ugly.

He knows it is time to consider other options before this
system implodes on itself.

Personally, I would like to see a PostGreSQL or MySQL backend
to either a Perl or PHP web interface. We are wide open for suggestions.
This includes commercial software as well.

He has been a die-hard Windows fan/user, however, he would consider
other options providing it meets his business needs and budget. I would like to hear
some suggestions providing they are in the context of this project.

v/r
-mike